The Giant Hummingbird is one of the most distinctive Neotropical bird species, although its general similarity to a swift or swallow in flight is often noted. Female and immature male Great Sapphirewings (Pterophanes cyanopterus) are the only hummingbird that could be potentially mistaken for Patagona. The distributions of Patagona and Pterophanes overlap slightly in Ecuador, Peru, and Bolivia, but Pterophanes prefers wetter habitats. Although its mass is approximately half that of Patagona, Pterophanes has disproportionately large wings and slow wingbeats that give it the appearance of a larger bird. Females of Patagona have entirely grayish-brown backs, as opposed to solid green in Pterophanes. Whereas Patagona has a distinctive white rump patch lacking in Pterophanes, Pterophanes females have pale outer webs to the outer rectrices that are lacking in Patagona.
Iris: Very dark brown, appearing black
Tarsi and toes: Very dark gray
Mass: Subspecies peruviana, males 21.1 - 25.2 g (mean = 22.7 ±1.9 SD), females 17.6 - 22.2 g (mean 20.4 ±1.4 SD) (MSB, MUSM, MVZ, CORBIDI specimen data).